Biogen (BIIB) shares soared 6.60% in pre-market trading on Thursday following the release of its impressive second-quarter 2025 financial results and an upward revision of its full-year outlook. The biotechnology company's performance exceeded analysts' expectations, driven by robust demand for its rare disease drugs and promising growth in its Alzheimer's treatment.

The company reported a second-quarter adjusted earnings per share (EPS) of $5.47, significantly surpassing the IBES estimate of $3.86. Revenue for the quarter reached $2.6 billion, outperforming the expected $2.323 billion. Biogen's strong performance was attributed to the success of its rare disease drugs, particularly Skyclarys, which helped offset declining sales of its older multiple sclerosis treatments.

In light of these positive results, Biogen raised its full-year 2025 guidance. The company now expects non-GAAP diluted EPS to range between $15.50 and $16.00, up from the previous forecast of $14.50 to $15.50. This optimistic outlook reflects an anticipated stronger business performance, despite some expected headwinds in the second half of the year. Biogen also revised its total revenue expectations for 2025, projecting approximately flat growth at constant currency, an improvement from the previously forecasted mid-single-digit decline. The company's Alzheimer's drug Leqembi showed promise, with U.S. sales reaching $63 million in the second quarter, indicating a 20% sequential growth. These factors combined to fuel investor confidence, resulting in the significant pre-market stock surge.